This invention relates generally to the separation of bitumen from tar sands and, more particularly, relates to the separation and recovery of bitumen from tar sands such as occur, for example, in the Athabasca tar sands (sometimes called oil sands) in Alberta, Canada, by flotation.
The original process for extraction of bitumen from the sands was developed by Dr. Karl Clark, working with the Alberta Research Council in the 1920s. Today, all of the producers doing surface mining, such as Syncrude Canada, Suncor Energy and Albian Sands Energy etc., use a variation of the Clark Hot Water Extraction (CHWE) process. In this process, the ores are mined using open-pit mining technology. The mined ore is then crushed for size reduction. Hot water at 50-80° C. is added to the ore and the formed slurry is transported using hydrotransport line to a primary separation vessel (PSV) where bitumen is recovered by flotation as bitumen froth.
The recovered bitumen froth typically consists of 60% bitumen, 30% water and 10% solids by weight. The recovered bitumen froth needs to be cleaned to reject the contained solids and water to meet the requirement of downstream upgrading processes. Depending on the bitumen content n the ore, between 90 and 100% of the bitumen can be recovered using modern hot water extraction techniques. After oil extraction, the spent sand and other materials are then returned to the mine, which is eventually reclaimed.
The economics of a process to recover bitumen by the CHWE process would benefit from an increased efficiency of the separation processes and from the recovery and reuse of at least some of the additives used to enhance the process.
The improved separation and recovery of bitumen from tar sands by the CHWE process would improve the feasibility and commercial viability of the process, especially if some of the additives used in the process could be recovered for reuse.
The separation of bitumen from tar sands at substantially ambient temperatures as described in U.S. Pat. No. 4,946,597, incorporated herein by reference in its entirety, obviated the need for the separation plant to be close to a supply of heat and permitted the separation of bitumen from the sands in proximity to the mining operation. This reduced the cost of transporting the solids, which comprise the bulk of the materials handled, since the separated sand and fine solids were now closer to disposal areas.
Conventional dry mining of tar sands for low-temperature bitumen extraction is accomplished by means of power shovels, draglines, bucketwheels and similar large earth moving equipment and the like. Wet mining can be accomplished in open pits by means of rotary excavators in combination with slurry pumps operating from a dredge or by waterjets in combination with mechanical equipment. Wet mining may also be used for deep deposits, by means of high pressure water jets in combination with slurry pumps in boreholes. An improved flotation process which operates at ambient temperatures, from above freezing to about 35° C., would provide the important advantage of permitting the choice of conventional dry mining techniques or wet mining techniques. The dry mining techniques employ hydraulic pipeline transportation of the mined tar sands to a separation plant. The wet mining techniques employ dredge mining, waterjetting or borehole mining with the option of hydraulic pipeline transportation of the tar sands to a separation plant or the processing of the tar sands on a dredge or adjacent a plurality of boreholes in an integrated mining and beneficiation operation with return of tailings directly to a tailings pond.
Dredge mining, waterjet mining in open pits or borehole mining of tar sands integrated with an improved ambient or low temperature flotation process would provide the important advantage of utilizing the shear energy consumed during the mining operation in water for initial disintegration of the tar sands and fragmentation of the bitumen for release from the sands preliminary to flotation.
The economics of a process to recover bitumen at low temperatures would also benefit from the recovery and reuse of at least some of the additives used to enhance the process.
The improved separation and recovery of bitumen from tar sands at ambient temperatures, i.e. “low temperatures” below about 35° C., would improve the feasibility and commercial viability of the process, especially if some of the additives used in the process could be recovered for reuse.